This invention relates to an electrographic recording process and apparatus, and more particularly a novel electrographic recording process and apparatus capable of electrostatically recording a picture on plain paper with a relatively low voltage.
With widespread use of facsimile equipment in recent years, it has been highly desired to provide facsimile equipment of small and economical type. Furthermore, it is also desirable to use inexpensive plain paper for the purpose of decreasing the operating cost. The term "plain paper" is used herein to mean ordinary inexpensive paper usually used in business. However, if it is desired to improve the quality of the reproduced facsimile picture the paper may be properly treated. Among the methods of using inexpensive plain recording paper are included electrophotography utilizing transfer printing of toner images and an ink jet recording apparatus. In electrophotography, the apparatus is complicated and bulky because it requires development, transfer printing and cleaning steps. On other hand, in the ink jet devices it is difficult to obtain flat bed scanning because of the mechanical scanning system and hence the recording speed and reliability are low.
As a method of obtaining a stable and high quality record by using relatively simple apparatus, an electrostatic recording process has been proposed which has been applied to facsimile equipments. However, according to the prior art electrostatic recording method an electrostatic latent image is formed by establishing an electric discharge through a microgap between an electrode and the recording paper so that it is necessary to use a recording voltage higher than 500 volts.
Furthermore, as the electrostatic latent image formed on recording paper is developed with a toner it is necessary to preserve the charge deposited at the time of forming the latent image until it is developed so that it is necessary to use special recording paper coated with a dielectric layer, thereby increasing the cost of recording.
Another electrographic recording apparatus in which a toner image is directly formed on a recording medium such as plain paper is disclosed in Kotz et al U.S. Pat. No. 3,816,840 entitled, "Electrographic Recording Process and Apparatus Using Conductive Toner subject to a Capacitive Force".